Heated die plate for making extruded pasta shapes

ABSTRACT

An apparatus for forming extruded pasta shapes. The apparatus is a die plate having a plurality of orifices wherein the die plate is heated, e.g., to a temperature of at least about 130 DEG  F. (about 54 DEG  C.), and preferably about 160 DEG  F. (about 71 DEG  C.) A coating is provided on only a portion of the interior surface of each orifice such that heat transfer to the paste is substantially inhibited in a given orifice until the cross section of the orifice has reached its smallest value.

This application is a division of U.S. Ser. No. 539,185, filed Jun. 18,1990, now U.S. Pat. No. 5,089,284.

FIELD OF THE INVENTION

The present invention concerns a process and an extrusion die for makingpasta by forming shaped alimentary pastes.

BACKGROUND OF THE INVENTION:

Pasta consumption is enjoying a rise in popularity for reasons ofhealth, nutrition, convenience and economy. Home consumers andrestauranteurs are therefore in need of a pasta product which isprepared in a very short amount of time without loss of palatability orflavor. Commercially available dry pasta takes 9 to 12 minutes to cookfor optimal tenderness. Once cooked, the pasta tends to become stickyand to lose a desirable mouthfeel upon standing for any period of time.

Another trend in food products is microwavable foodstuffs, because ofthe great savings of time and waste for the consumer. It is known in theart to prepare microwave cooked pasta. For example, Golden GrainMacaroni Company markets a product which is cookable in warm water. Itspackage directions require placing pasta in warm water; microwaving toboiling; continued boiling for three minutes to absorb water; andflavoring with a cheese sauce. However, the boiled pasta suffers greatstarch loss and is only palatable when sauce is added to the boiledproduct to mask its gumminess and starchiness.

It is also known in the art to prepare an uncooked pasta product whichis tolerant of an initial exposure to room temperature or colder water.This allows the pasta to be microwave cooked by adding non-boilingwater, inasmuch as the pasta product is pretreated in such a way as tostabilize it against starch leaching when exposed to cold water.Specifically, such pasta, which is the subject of a U.S. patentapplication of Chawan et al., Ser. No. 225,211, filed Jul. 28, 1988, nowabandoned and assigned to the assignee of the present invention,experiences a starch loss, after cooking, of less than about 7.0% byweight of the uncooked pasta.

A continuation-in-part of that application, U.S. Ser. No. 485,893, filedFeb. 28, 1990, issued as U.S. Pat. No. 5,063,072.

That application teaches that one way by which such cold water tolerantpasta may be prepared is to subject it, after shaping, to a hightemperature treatment, i.e., at least about 180° F. (about 82° C.). Suchtreatment may be accomplished in any of a number of ways, includingtreatment in a dryer (e.g., a hot air, humidity controlled circulatingoven), microwave oven, heated drum, infrared tunnel, dielectric heater,or by contact with superheated steam. Preferably, however, the hightemperature treatment is performed using a tres haute temperature (THT)drier, such as the one disclosed in Pavan U.S. Pat. No. 4,699,048.

While such treated pasta has the desirable property of microwavecookability due to its cold water tolerance, its processing isundesirable in that it requires additional and expensive equipment,i.e., a drier capable of tres haute temperature drying. Such dryers maycost as much as one million to three million dollars.

It is also known, as in Katz et al., U.S. Pat. No. 3,138,462, to heat anentire pasta extruder to temperatures as high as 140° C. (about 284°F.). However, that patent is concerned with the extrusion of alreadycooked or gelatinized pasta, the heating probably being performed inorder to avoid clogging of the die. Furthermore, this patent does notaddress the issues of cold water tolerance and microwave cookability.

It is further known in a pasta extrusion process, as U.S. patentapplication Ser. No. 39,744 to Ventres et al., filed Apr. 20, 1987,assigned to the assignee of the present invention, to heat the die head,or throat portion, of an extrusion die, upstream of the die plate to atemperature which approximates the temperature of the alimentary pastewithin the extruder. However, inasmuch as the heating takes placeupstream of the paste-shaping die orifices, no effect is experienced bythe already formed pasta shapes.

SUMMARY OF THE INVENTION

This invention is thus directed to a process and an extrusion die forpreparing extruded pasta shapes which are, inter alia, capable ofmicrowave cooking. More specifically, the invention pertains to a methodusing a heated extrusion die plate, and to an extrusion die plate whichcan be heated to a temperature of at least about 130° F. (about 54° C.).

In one embodiment, the invention is a method of forming extruded pastashapes by feeding a feedstock comprised of glutinous flour and water toan extruder that is equipped with a die plate having a plurality ofholes, and extruding said alimentary paste through the holes in theextruder die plate by internal pressure. Extrusion is performed in sucha manner that the extruded pasta shapes remain substantially uncooked.The improvement provided by the invention comprises heating the extruderdie plate to a temperature of at least about 130° F. (about 54° C.), andpreferably about 160° F. (about 71° C.), in order to attain theadvantages of the invention.

The invention further comprises a method of forming pasta shapes byfeeding a feedstock comprised of glutinous flour and water to anextruder that is equipped with a die plate having a plurality of holeswhose cross sections preferably decrease in the direction of extrusion.The alimentary paste is extruded through the holes in the extruder dieplate in such a manner that the extruded alimentary paste remainssubstantially uncooked. The improvement provided by the inventioncomprises heating the die plate to a temperature of at least about 130°F. (about 54° C.) and preferably about 160° F. (about 71° C.), andpreferably providing a coating on a portion of the interior of the holesthrough the die plate such that heat transfer to the paste beingextruded is substantially inhibited until the cross section of the holehas been reduced, and preferably has reached its smallest value.

In other aspects, the invention is an extruder die plate which may beheated to the above described temperatures, and which may have a coatingas above described. Preferably, the die plate is equipped with internalheaters to achieve the requisite heating, as described hereinafter.

In other preferred embodiments, the alimentary paste further containsbetween about 0.5 weight percent and about 10.0 weight percent of a lowtemperature coagulatable protein material, and the hole coating materialis a plastic having a low coefficient of friction and low thermalconductivity, e.g., polytetrafluoroethylene or polyvinylidene fluoride.

In yet other aspects, the invention is extruded pasta shapes preparedusing the die plate and method of the present invention.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a schematic end view of the heated die plate of the invention,showing means for heating.

FIG. 2 is a schematic side elevation of the heated die plate, having acut-away portion showing detail of a die orifice.

DETAILED DESCRIPTION

This invention pertains to economical and efficient processes forpreparing an alimentary paste for shaping by extrusion into pastashapes, which pasta is microwave cookable without substantial starchleaching.

The invention is, inter alia, a method of forming shaped alimentarypastes by feeding a feedstock comprised of glutinous flour and water toan extruder that is equipped with a die plate having a plurality ofholes, and extruding said alimentary paste through the holes in theextruder die plate by internal pressure. Extrusion is performed in sucha manner that the extruded alimentary paste remains substantiallyuncooked, i.e., less than about 20% of its starch content isgelatinized. The invention comprises heating the extruder die to atemperature of at least about 130° F. (about 54° C.) in order to attainthe advantages of the invention.

Conventional pasta preparation is a fairly time-consuming process forthe consumer, taking at least about fifteen minutes. Before the pastaencounters water in which it is to be cooked, the water must be at ornear the boiling point in order to set gluten in the pasta and preventleaching of the starch. The cooking process then typically requiresabout 9 to 12 minutes, after which the cooking water must be drained.

It is a surprising advantage of the present invention that it ispossible to subject uncooked pasta to room temperature or colder waterfor a brief period of time, and subsequently cook the resulting pastafor a short period of time, e.g., by microwave energy, withoutsubstantial loss of starch into the water.

It has been found that when, in the course of extrusion, alimentarypaste, which inherently contains protein in the form of gluten, issubjected to a temperature of at least about 130° F. (about 54° C.), theprotein component which surrounds the starch granules, and which iswater soluble in its native form, at least partially denatures,resulting in its effectively encapsulating the starch granules byforming a water insoluble protein matrix in which the starch isentrapped. This matrix renders the extruded pasta shape stable againststarch leaching in the presence of cold water, at least for shortperiods of time. Conventional pasta that has not been subjected to thishigh temperature denaturation must immediately contact extremely hot(preferably boiling) water in order to set the protein matrix;otherwise, the starch will rapidly leach out into the cooking water,resulting in a mushy, gummy, unsatisfactory product.

The result in the present invention is a storage-stable, still uncookedextruded pasta shape which has the unique advantage of being able towithstand exposure to non-boiling water, without leaching starch intothe water, for a period of at least about ten to about fifteen minutes.This confers to the pasta shape the property that it may be microwavecooked without first exposing it to boiling water. Thus, the actualcooking process may be accomplished in only about six to about tenminutes.

Uncooked pasta may be prepared from any formulation known in the art. By"uncooked " is meant pasta wherein a major portion, i.e., greater thanabout 80% by weight of the total starch content, is ungelatinized (i.e.,less than about 20% gelatinization). The term "cooking " as used hereinrefers to the process of gelatinizing the starch and heating the pasta.

Pasta is prepared by shaping an "alimentary paste " or dough by which ismeant a glutinous flour and water mixture. Alimentary pastes or doughsare generally made from coarse, hard flours obtained from hard wheatsuch as the middlings of durum wheat, often referred to as "semolinaflour " or "semolina ". In addition, fine flours such as durum flour,wherein 98 weight percent passes through a 70 mesh sieve, are alsosuitable and are intended to fall within the scope of the term"glutinous flour ". The only requirement for the flour is that itprovide a self supporting paste.

A typical alimentary paste used to prepare pastas suitable for thepresent invention comprises, based on the weight of uncooked pasta,between about 67.0% and 80.0% by weight (solids basis) of semolina flour(having an inherent moisture content of between about 10% and about 15%and preferably between about 11% and about 14% by weight, and a glutencontent of between about 11% and about 14% by weight), the balance beingoptional additives and added water.

More specifically, then, a suitable paste may be prepared from 10 kgfancy durum patent flour and about 2200 grams of added water; a lowermoisture formulation may be prepared by adding about 1500 grams of addedwater to the same amount of flour.

Several additives may be added to the flour/water alimentary pastessuitable for use in the present invention. Some suitable additivesinclude glycerol monostearate (GMS); an added low temperaturecoagulatable protein material; a sulfhydryl reducing agent; and addedvitamins typically added to enrich food products, e.g., B-vitamins. Asuitable normal or lower moisture paste as described above mightadditionally include, e.g., 2.5 grams of cysteine.

In a preferred embodiment, a low temperature coagulatable proteinmaterial, distinct from the gluten component inherent in the glutinousflour, is added. These protein materials are ones which coagulate (i.e.,denature) at temperatures of about 140° F. (about 60° C.) or above. Theexact temperature at which the protein denatures is dependent on variousfactors including moisture content; higher moisture contents requirelower temperatures to denature the protein material. The added proteinmay serve to enhance resistance to starch leaching in the presentinvention. Additionally, it may improve the texture and/or flavor of theproduct, such as when egg noodles are desired. The protein component, ifused, must be denaturable at the temperature to which it will be exposedin the heated die of the present invention, in order to contribute tothe benefits of the present invention.

The added proteins include, but are not limited to, albumin, whole egg,egg white, egg yolk, whey protein concentrate, and mixtures thereof. Anyof these protein materials may be added dry or as is. A preferredprotein material is egg white. When used, the added protein componentcomprises up to about 10.0% by weight of the total paste, i.e., betweenabout 0.5% and about 10.0%, and preferably between about 0.5% and about3.0% by weight based on the alimentary paste.

The remainder of the paste comprises water. Water is preferablyintroduced in the form of ice before or during extrusion, to preventswelling of the paste during extrusion. The water, or moisture, contentis preferably between about 20.0% and about 30.0% by weight of thepaste. In this application, water or moisture content refers to totalmoisture, that is, inherent moisture, or moisture naturally present inthe flour and other ingredients, as well as added water. The term "water" as used herein includes water in all physical states, i.e., steam, iceor liquid water, or mixtures thereof.

The flour, water and any additives used may be mixed in any wayconventional in the art, such as by mixing in a vertical cutter mixer(e.g., a Hobart Cutter/Planetary Mixer) for approximately one minute, atwhich time the pasta dough is ready for extrusion in any of theconventional pasta shapes. Alternatively, the components of the pastemay be separately introduced into an extruder without prior mixing.These extruded pasta shapes are then preferably subjected to a dryingstep, discussed below.

Shaped pasta is prepared from the paste by extrusion. Extrusion can beperformed with any acceptable extruder whose die has been modified inaccordance with the invention. The alimentary paste is fed into theextruder wherein it may, optionally, be blended, in the case of ascrew-type extruder, or further blended, if the feedstock was premixedbefore being fed into the extruder, and then forced by internal pressurethrough the holes of the extruder that is equipped with a die platehaving a plurality of holes to obtain the desired shape. The holes ofthe die plate have cross sections o which decrease, e.g., in stepwisefashion, in the direction of extrusion. The holes in the extruder dieplate prescribe the profile of the extruded pasta shape. Such shapesinclude spaghetti, fettucine, linguine, rotini, elbows, spirals, shells,ziti, vermicelli, fusilli, tortellini, ravioli, manicotti, lasagne,rote, tortiglioni, or the like.

The alimentary paste may pass through the die plate due to internalpressure generated by a rotating screw or screws. Suitable screw speedsrange from about 3.5 to 14 revolutions per minute (rpm), and preferablyabout 3.5 rpm to 10.5 rpm. A particularly optimal screw speed is about3.5 rpm. In general, screw speeds in excess of about 14 rpm appear toresult in compromised texture and increased starch loss in the pastaproduct, whereas screw speeds of less than about 3.5 rpm render theextrusion process economically unfeasible.

The screw speed is chosen to result in an extrusion rate, for example,in the range of about 50 grams per minute (g/min) to about 500 g/min orgreater, preferably about 175 g/min, based on a six-orifice die havingapproximately two inch-deep orifices.

Optimized extrusion rate appears to be correlated to, inter alia, dieplate temperature, barrel temperature and screw speed. For example, at ascrew speed of 3.5 rpm and at barrel temperatures of 110° F. and 120°F., respectively, acceptable extrusion rates of 62 and 55 g/min,respectively, result. Whereas, at 110° F. and 10.5 rpm, an acceptableextrusion rate of 175 g/min occurs.

If the extrusion rate is significantly higher than the specified maxima,the texture of the product will suffer, due to excessive shear andgelatinization, and cooking loss will increase.

Vacuum pressure may or may not be used. If used, a pressure of about 40cm Hg to about 60 cm Hg, preferably about 40 cm Hg, may be used.

One particular advantage of the present invention over prior artextrusion processes is the reduction in pressure on the die orificerequired, and concomitant cost savings, of the present process. Whereasconventional processes may require, at a barrel temperature of about110° F. (about 43° C.), at least about 4500 psi internal (die orifice)pressure, the present process may be performed satisfactorily atpressures in the range of about 2500 psi to 3000 psi at thattemperature. This facilitation is most likely a result of a viscositydecrease of the heated extruded paste as it passes through the dieplate.

Power savings relative to prior art extrusion processes are about 4% to7%, based on amperage used. Typical power usage in the present inventionis in the range of about 10 amps to about 15 amps, preferably about 12amps to about 13 amps. However, power usage is, like other parameters,rate dependent; higher power use is related to higher extrusion rate.

Conventional extrusion processes typically require about 15 amps toabout 20 amps; this reduction in power use results in a significant andunexpected cost savings relative to prior art processes.

Typical extruder conditions include a barrel temperature of about 70° F.to about 120° F. (about 21° C. to about 49° C.), preferably about 100°F. (about 38° C.) to about 120° F. (about 49° C.). A screw temperaturein the same range is preferred. Preferably, a vacuum of 26 to 76 cm Hgis applied, and a die orifice pressure of 1500 psi to 3000 psi is used.

For optimal extrusion, the barrel temperature of the extruder should beapproximately 120° F. (about 49° C.), and the extruder should have about40 to about 60 cm of mercury vacuum; a power delivery of 5 to 10 amps;and a die orifice pressure of 1800 to 2700 psi.

Extruders which have been found acceptable include the DeMaco-S25extruder, the Mapimipianti GF20 extruder and other commerciallyavailable extruders marketed by Brabender, Buhler or Braibanti.

It should be mentioned here that the present invention has been seen topermit decreased operating costs relative to the prior art due, interalia, to decreased amperage requirements; this and other advantages willbe discussed in further detail hereinbelow.

A suitable extrusion process is a so-called low moisture, hightemperature process, i.e., one where the final moisture content of theresulting pasta is between about 20% and about 28% by weight, based ontotal moisture in the pasta. Such a process is disclosed in U.S. Ser.No. 39,744, to Ventres et al., filed Apr. 20, 1987, assigned to theassignee of the present invention. That application is hereinincorporated by reference.

The present invention also pertains to an extrusion die plate forforming extruded pasta shapes which is modified to carry out the methodof this invention.

The modification of the extrusion apparatus in accordance with thisinvention comprises a means for heating the die plate thereof. The dieplate may be modified in any practical manner such that it may be heatedto a temperature of at least about 130° F. (about 54° C.), e.g., in therange of about 130° F. (about 54° C.) to about 200° F. (about 93° C.)and preferably about 140° F. (about 60° C.) to about 180° F. (about 82°C.), preferably by means of integral heating means, e.g.,thermostatically controlled electrical resistance heaters. Morepreferably, the die plate has a temperature in the range of about 150°F. (about 66° C.) to about 160° F. (about 71° C.),

e.g., about 160° F. (about 71° C.). In general, at higher screwspeeds/higher extrusion rates, a higher die plate temperature (i.e.,about 180° F. or about 82° C.) is still very acceptable.

Although the extruded pasta is exposed to heat, the heating is of shortenough duration that the extruded pasta remains substantially uncookedsuch that less than about 20% of its starch content is gelatinized. Thisparameter is important inasmuch as best quality pasta, in terms oftexture and shelf life, results when the pasta's starch is ungelatinizedyet encompassed in a protein matrix.

This heating may be achieved, for example, by providing the die platewith one to six core heaters, preferably six, of about 100 to about 400watts each, e.g., about 400 watts each, the temperature of which may becontrolled with a setpoint thermostat. Alternatively, each profile maybe heated individually by supplying heat to each hole, e.g., throughresistance wires.

Turning to FIG. 1, a schematic end view of the outer face of the dieplate with integral heating means is shown. Uncooked alimentary pastepasses through die orifices 1-6 (shown in phantom in FIG. 1 as twoconcentric circles to indicate the progressively decreasing diameter ofthe orifices in the direction of extrusion) during which time it isexposed to heat supplied by core heaters 7-9, heated by resistanceheaters, not shown. Numerals 10-15 indicate the end portions of orifices1-6, showing that the diameter of the orifices decreases in thedirection of extrusion. Collar 16 secures the die plate to the extruder.

The heating of the die plate, of course, results in an increasedtemperature of the extruded alimentary paste. Looked at in another way,the apparatus is modified so as to produce an alimentary paste which,when extruded through the die plate, has an average temperature in therange of about 120° F. (about 49° C.) to about 165° F. (about 74° C.)and preferably about 130° F. (about 54° C.) to about 150° F. (about 66°C.), e.g., about 140° F. (about 60° C.). In general, die platetemperature and screw speeds may be varied so long as the averageproduct temperature does not rise above about 165° F. (about 74° C.).

The optimal temperature range for either the die plate or the pastedepends on other processing parameters such as extrusion rate, pressure,moisture content, etc. For example, it has been observed that, as screwspeeds are increased, higher die temperatures are tolerable and evenpreferable.

The die plate comprises a number of die orifices (holes) through whichthe pasta is extruded. Preferably, the die orifices are tapered, suchthat their cross sections decrease (e.g., from about 0.25 in. to about0.063 in.) in the direction of extrusion. In one embodiment, the crosssection decreases in one or more step-down sections.

In a particularly preferred embodiment, at least a portion of the holesof the die orifice are lined with a stick-resistant surface, having alow coefficient of friction and low thermal conductivity, e.g. a coatingmaterial selected from polyvinylidene fluoride andpolytetrafluroethylene. A particularly preferred coating materialcomprises polytetrafluoroethylene ("TEFLON ", from DuPont, Wilmington,Delaware). The innermost face of the die plate is also preferablyinsulated in order to prevent transfer of heat to the unextruded paste.

The coating on a portion of the orifices serves to substantially inhibitheat transfer to the paste being extruded until the cross section of thehole reaches its smallest value, e.g., by coating all but about the last10% to 25% of the orifices, e.g., the last 1/4 inch of the orifices,which appears to be beneficial to the process for the reason discussedbelow.

FIG. 2, which depicts a side view of the die plate, shows, in thecut-away section, the embodiment wherein all but the last portion of thedie orifice is coated. The arrow indicates direction of extrusion. Dieorifices 1-4 have progressively smaller cross sections in the directionof extrusion. The cross hatched portion shown in the cut-away representsa thin (e.g., 0.04") plating of coating material such as polyvinylidenefluoride which coats all but the portion of the orifice of smallestcross-section. These uncoated end portions 10-13 are the portionswherein heating of the paste actually occurs.

It has been observed that optimal properties result when as little aspossible of the extruded product (i.e., 20% by weight or less) isgelatinized. This is what is generally meant by the description,"substantially uncooked. " Thus, best results are obtained if thesmallest practicable volume of the pasta shape, i.e., if only theoutermost "shell " of the pasta, is gelatinized. While not wanting to bebound by any particular theory, it appears that an optimized productresults if the matrix of the paste is allowed to continue mixing for thelongest possible period of time; this preferred embodiment allows thisto happen by delaying surface gelatinization and the subsequentformation of a hard outer "corona " or shell until effectively the lastpossible moment.

Although FIG. 2 shows the cross section decreasing in a continuousfashion, the cross section of the die orifices may decrease from theback to the front of the die plate in several step down sections. As thepaste passes through these sections, it has a tendency to fold overitself so that the paste which is heated from contact with the wall ofthe die orifice would be folded into the center of the pasta.

By coating most of the interior of the orifice, the paste being extrudedhas direct thermal contact with the heated die plate only in the lastsection of the die orifice which has the smallest (final) cross section,thus helping to restrict gelatinization to this outermost "corona "region of the shape. By acting as a partial thermal insulator, thecoating substantially inhibits heat transfer to the paste within thecoated section of the bore until the cross section of the hole hasreached its smallest value, thus exposing the paste to the highertemperature only in the last section of the hole. This apparently servesto partially gelatinize the outer portion of the shaped pasta withoutgelatinizing the core, to obtain the desired result of minimal, i.e.,less than about 20%, gelatinization.

The extruded pasta shapes may, optionally, be cut to desired lengths toprovide a product in substantially final form. Cutting generally occursat the extruder die and may be carried out in a conventional manner.Cutting is not essential to the practice of this invention since thepasta shape may be formed into desired lengths by merely pulling theextrudate away from the die.

The shaped and cut pasta may then be subjected to a drying step, asknown in the art, to lower its moisture content from between about 20%and about 30% by weight down to between about 10% and about 15%, andpreferably between about 11% and about 14%, based on the weight of thedried pasta. Traditionally, pasta is dried at a temperature of about110° F. (about 43° C.) dry bulb, and about 100° F. (about 38° C.) wetbulb, for about 14 to about 36 hours.

The resulting pasta may then be packaged, preferably in packaging whichis shelf stable, in any way known in the art, but preferably inpackaging which is microwave safe and penetrable so that the pasta maybe prepared directly in its package. Such packaging includes paper (e.g.cardboard), glass or plastic. The packaging may comprise individualportions (e.g., of 3 to 4 ounces each) or bulk portions (e.g., of 5 to10 pounds) for institutional use. By shelf stable is meant that thepackaging protects its contents from degradation under non-refrigeratedconditions, i.e., above 40° F. (about 4° C.), for a time period of up toabout 36 months' time.

Such microwave cookable prepackaged product may be prepared forconsumption by adding non-boiling water or other liquid, e.g., hot tapwater, directly to the package itself. The amount of added water shouldbe sufficient to hydrate the pasta but preferably small enough that,after cooking, all of the liquid is absorbed into the product so thatdraining of excess water is not necessary.

Microwave cooking then may be accomplished by microwave heating at apower level of about 600 to about 750 watts, for a period of time fromabout eight to about ten minutes.

Several unexpected results follow from the aforedescribed method, inaddition to the aforedescribed objective, i.e., rendering the pastaamenable to various processing conditions such as microwave cooking.

Significantly, from an economic standpoint, it has been discovered thatit is possible to increase the production rate and to decrease extrusionhead pressures, relative to prior art processes, by employing the heateddie plate of the present invention. Also, decreased amperages may beused with the increased die plate temperatures; these phenomena areprobably the result of a slight decrease in viscosity due to theaddition of heat, thus facilitating extrusion to some degree.

Also very significant are the quality characteristics of the shapedalimentary pastes which result, even at the aforedescribed reducedextrusion pressures and power usage of the invention. The extruded pastashapes prepared using the aforedescribed die and method are also part ofthe present invention.

It has surprisingly been found that cooking losses from pasta productsprepared using the heated die plate of the present invention are lessthan about 8%, and preferably less than about 7% by weight. These starchlosses are comparable to those experienced by the more capital intensiveprocesses disclosed in the 10 aforedescribed United States patentapplication Ser. No. 225,211 of Chawan et al., which require expensiveapparatus such as a tres haute temperature drier, in order to accomplishthe requisite heating.

Moreover, there is an apparent improvement in the color of the cookedproduct relative to conventionally extruded pasta. Specifically, abrighter yellow color was observed with increased die plate temperature,which was deemed desirable. This was probably a result of the starchgelatinization at the surface which had occurred.

Additionally, the texture of the extruded product appears to improvewith increased die plate temperature. This is probably an indirectresult of the lower retention time effected by the heating. The loweredretention time results in faster production time, resulting in lessstarch damage during processing.

Product texture may be further improved by insulating the die plate, asdescribed above, so that heating only occurs as the alimentary pastecrosses the narrowest cross section of the die orifice.

The following Examples are provided to further illustrate the invention.In these Examples and throughout the specification, all temperatures areexpressed in degrees Fahrenheit and each value is accompanied by anapproximation of such value in degrees Celsius. In addition, allpercentages are by weight, unless expressly indicated to be otherwise.

EXAMPLE 1

An alimentary paste was made up using SO₂ treated semolina flourcombined with water using a Hobart vertical cutter to make a pastehaving a total moisture content of 26%.

A Mapimipianti GF20 extruder was used, which had a die plate havingtapered die orifices, as depicted in FIGS. 1 and 2. The die plate wasmodified for heating by modifying a conventional die plate as follows.First, all holes of a twelve-orifice die were plugged, and six of theholes redrilled with a 0.03 inch drill to make the six die orifices.0.50 inch holes were drilled for accommodating resistance heaters. Theinner face and orifices were then plated with polyvinylidene fluoride,and the ends drilled out with a 0.03 inch drill. The die orifices were2.063 inches deep, the last 0.25 inches of which were uninsulated, theremainder being insulated with polyvinylidene fluoride. The insideradius of the tapered die orifices decreased from 0.22 ins. to 0.03 ins.at its end.

In this Example, the temperature of the extruder barrel was controlledat 110° F. (about 43° C.). The screw speed was controlled at 3.5 rpm.The resulting extrusion pressure was 4290 psi, and the power was 15.25amps. An extrusion rate of 41 g/min. was observed.

A thermostat controlling the heaters in the die plate was set at 140° F.(about 60° C.) to attain an actual temperature of 134° F. (about 57°C.). These temperatures were measured using an infrared thermometerbetween the die surface center and the outside of the extruded strand.

Product temperature was measured to be 135° F. (about 57° C.), using apolyvinylchloride (PVC) elbow to collect a sample of extrudate, andmeasuring the temperature of the sample collected.

A retention time of 0.18 seconds was calculated for the uninsulatedportion of the die, and of 1.45 seconds for the entire die. Retentiontime was measured by collecting a length of extrudate extruded in oneminute, measuring the mean length in inches ÷60 seconds, and solving forD=V×t, where D=length of either the uninsulated section (0.25 in), or ofthe total die (2.063 in.)

The resulting pasta shape was dried while cycling the dry bulbtemperature from 40° C. to 57° C. to 25° C. and cycling the relativehumidity from 50% to 77% to 50%.

The resulting pasta shape (thin spaghetti) was cooked by the followingmethod: 50.0 grams of pasta was added to a four-quart saucepancontaining 1500 grams of boiling distilled water, 15 seconds after thewater came to a boil. Fifteen seconds later, after all contents had cometo a boil, a 12 minute timer was set. After 12 minutes, the pasta wasremoved from the heat, drained and allowed to sit for one minute beforeevaluation.

A texture rating of 4.0, on a scale of 1.0 to 5.0, was assigned to thecooked product, indicating very good 30 texture. (In the texture ratingscale, 1.0 indicates poor texture, 3.0 indicates acceptable texture, 4.0indicates very good texture, and 5.0 indicates excellent texture.) Apercentage starch loss of 6.2% was measured, by dividing the product ofthe percent solids in the drain water times drain water weight, by theinitial weight of the uncooked pasta.

EXAMPLES 2-3

The process of Example 1 was essentially repeated, except that thetemperature setting for the thermostat controlling the die plate wasincreased to 160° F. (about 71° C.) in Example 2 and to 180° F. (about82° C.) in Example 3, to attain actual temperatures of 148° F. (about64° C.) in Example 2 and of 158° F. (about 70° C.) in Example 3. Thebarrel temperature was again 110° F. (about 43° C.). In both Examples 2and 3, the extrusion pressure was 3725 psi.

The product temperatures were measured to be 136° F. (about 58° C.) inExample 2, and 144° F. (about 62° C.) in Example 3. Extrusion rates of48 g/min and 61 g/min were employed for Examples 2 and 3, respectively.

Die retention times of 0.14 seconds for the uninsulated portion of thedie, and of 1.17 seconds for the whole die were measured in Example 2;and of 0.11 seconds and 0.92 seconds in Example 3.

The extruded product, after drying and cooking had, in both cases, atexture rating of 3.5, indicating acceptable texture, and percentagestarch loss of 7.4% (Example 2) and 7.5% (Example 3).

EXAMPLES 4-6

Again, the process of Example 1 was substantially repeated, except thatthe barrel temperature setting was increased to 120° F. (about 49° C.)for each of Examples 4-6. After increasing the barrel temperaturesetting, the extruder was allowed to equilibrate for 40 minutes.

Power, extrusion pressures, and die (plate) temperature thermostatsettings were varied in each of Examples 4-6. These values aresummarized below:

    ______________________________________                                                 Example 4                                                                              Example 5   Example 6                                       ______________________________________                                        Power (amps)                                                                             12.25      13.25       12.75                                       extrusion  3775       3290        3025                                        pressure (psi)                                                                die temperature                                                                          140° F.                                                                           160° F.                                                                            180° F.                              setting    (60° C.)                                                                          (71° C.)                                                                           (82° C.)                             actual die 140° F.                                                                           155° F.                                                                            168° F.                              temperature                                                                              (60° C.)                                                                          (68° C.)                                                                           (76° C.)                             ______________________________________                                    

Product temperatures were measured to be 132° F. (about 56° C.); 143° F.(about 62° C.); and 153° F. (about 67° C.), respectively, and extrusionrates, 37 g/min; 51 g/min; and 57 g/min; respectively, for Examples 4-6.Die retention times were measured, for the uninsulated portion and forthe whole die, to be 0.20 seconds and 1.61 seconds for Example 4; 0.13seconds and 1.05 seconds for Example 5; and 0.12 and 0.98 seconds forExample 6.

The extruded products had texture ratings of 3.0; 3.5; and 3.0,respectively, and percentage starch losses of 6.8%; 7.7%; and 7.4%,respectively, for Examples 4, 5 and 6.

EXAMPLE 7

The process of Example 1 was followed, except that, inter alia, thescrew speed was increased to 10.5 rpm, and the barrel temperature, to120° F. (about 49° C.). Power of 15.5 amps; an extrusion pressure of3825 psi; and an extrusion rate of 175 g/min were recorded.

The die thermostat temperature was set at 200° F. (about 93° C.) toattain an actual temperature of 177° F. (about 81° C.), and the producttemperature was measured as 160° F. (about 71° C.).

Die retention time was 0.05 seconds in the uninsulated portion of thedie and 0.38 seconds for the entire die.

The extruded product had a texture rating of 3.0 and a starch loss of6.9%.

EXAMPLE 8

This Example shows that deleterious effects regarding starch loss ensuewhen the temperature of the heated die plate is below the temperaturerange claimed in the present invention.

The procedure of Example 1 was substantially repeated, except that thedie temperature thermostat was set at 120° F. (about 49° C.), to attainan actual die temperature of 126° C. (about 52° F.).

Power was measured at 16.25 amps, extrusion pressure at 5700 psi, andextrusion rate at 32 g/min.

The temperature of the extruded product was measured at 124° C. (about51° C.), and the die retention times as 0.23 seconds (uninsulatedportion) and 1.89 seconds (entire die).

The product had a texture rating of only 2.5, indicating fair texturalproperties, and an unacceptably high starch loss of 10.9% by weight.

EXAMPLE 9

Like Example 8, this Example shows the deleterious effects of low dieplate temperature.

Similar to Example 5, in this Example, a screw speed of 3.5 rpm; barreltemperature of 120° F. (about 49° C.); and power of 13.25 amps wereused. The extrusion pressure was 4490 psi, and the extrusion rate was 24g/min. The die thermostat was set at 120° F. (about 49° C.) (actual 122°F., or about 50° C.) and the product temperature was also 122° F. (about50° C.). Retention times were 0.28 seconds (uninsulated) and 2.34seconds (entire).

The extruded product had a texture rating of only 2.5 and a starch lossof 8.9%.

EXAMPLE 10

This Example shows that, at higher extrusion rates, higher die platetemperatures produced an acceptable or nearly acceptable product.

The procedure of Example 8 was repeated except that the die platetemperature was set at 200° F. (about 93° C.) to attain an actual dietemperature of 186° F. (about 86° C.). Power was 15.0 amps; extrusionpressure, 2975 psi; and extrusion rate, 65 g/min. The extruded producthad a temperature of 154° F. (about 68° C.), and die retention timeswere measured as 0.10 seconds (uninsulated) and 0.85 seconds (entire).The resulting product had a acceptable texture rating of 3.5, and anonly slightly high starch loss of 8.2%.

EXAMPLES 11 AND 12

The following Examples show that, at higher extrusion rates, high dieplate temperatures are acceptable.

Again, the process of Example 1 was essentially followed, except that,in Example 12, a screw speed of 6.25 rpm was used, and, in both of theseExamples, a die temperature setting of 200° F. (about 93° C.) was used,to attain an actual die temperature of 190° F. (about 88° C.) in Example11, and of 182° F. (about 83° C.) in Example 12.

In Example 11, the power used was 12.75 amps; the extrusion pressure was2675 psi; and the extrusion rate was 65 g/min. In Example 12, thesevalues were 14.5 amps; 3275 psi; and 109 g/min, respectively. (Theextrusion rate in Example 12 was about 1.7 times that of Example 11.)

Retention times were 0.10 seconds (uninsulated) and 0.85 seconds(entire) in Example 11, and 0.06 seconds (uninsulated) and 0.52 seconds(entire) in Example 12. Product temperatures of 163° F. (about 73° C.)and of 156° F. (about 69° C.), were measured in Examples 11 and 12,respectively.

The product of Example 11 had a textural rating of 2.5 and a starch lossof 9.7%. The product of Example 12 (wherein the die temperature wasactually only about 182° F.) had a textural rating of 3.0 and a starchloss of 8.2%.

EXAMPLES 13-21

The following Examples were conducted to show the effects on producttexture and cooking loss of varying the screw speeds along withtemperature.

In each of Examples 13-21, mix moisture was 26%, the barrel temperaturewas 120° F. (about 49° C.), and drying was achieved as in Example 1.

Screw speeds; power; extrusion pressure and rate; extrudate velocity;die plate temperatures (settings and actual); product temperatures;texture rating; and cooking losses and listed for each of Examples 13-21in the Table which follows.

    __________________________________________________________________________                                Actual                                                Screw    Extrusion                                                                          Extrusion                                                                          Die  Die  Prod.                                                                              Extrudate  %                                speed                                                                             Power                                                                              pressure                                                                           rate setting                                                                            temp.,                                                                             temp.,                                                                             Velocity,  Starch                       Ex. #                                                                             (rpm)                                                                             (amps)                                                                             (psi)                                                                              (g/min)                                                                            °F.                                                                         °F.                                                                         °F.                                                                         ft./min.                                                                            Texture                                                                            loss                         __________________________________________________________________________    13  6.25                                                                              13-14                                                                              3375 135  160  158  139  11.5  3.0  8.2                                                 (71° C.)                                                                    (70° C.)                                                                    (59° C.)                              14  10.5                                                                              13-14                                                                              4125 195  160  146  140  16.8  3.0  8.2                                                 (71° C.)                                                                    (63° C.)                                                                    (60° C.)                              15  14.0                                                                              13-14                                                                              4500 295  160  153  148  25.0  3.5  8.8                                                 (71° C.)                                                                    (67° C.)                                                                    (64° C.)                              16  6.25                                                                              12-13                                                                              3000 170  180  168  149  15.3  3.0  8.6                                                 (82° C.)                                                                    (76° C.)                                                                    (65° C.)                              17  10.5                                                                              14-15                                                                              3800 245  180  172  149  19.3  3.0  8.1                                                 (82° C.)                                                                    (78°  C.)                                                                   (65° C.)                              18  14.0                                                                              14-15                                                                              3825 345  180  171  153  28.7  3.5  8.3                                                 (82° C.)                                                                    (77° C.)                                                                    (67° C.)                              19  6.25                                                                              10-12                                                                              2750 180  200  186  160  18.0   3.0+                                                                              9.5                                                 (93° C.)                                                                    (86° C.)                                                                    (71° C.)                              20  10.5                                                                              12.5-14                                                                            3300 270  200  188  156  26.5  3.5  8.1                                                 (93° C.)                                                                    (87° C.)                                                                    (69° C.)                              21  14.0                                                                              13-14                                                                              3675 390  200  189  159  34.5   3.5+                                                                              8.0                                                 (93° C.)                                                                    (87° C.)                                                                    (71° C.)                              __________________________________________________________________________

These data appear to show that, at higher screw speeds, higher die platetemperatures are feasible and are not particularly deleterious to theproduct in terms of texture and starch loss.

EXAMPLES 22, 23 and 24

Three samples, resulting from Examples 14, 17 and 20 above, were testedfor microwave cookability.

In Example 22, 123 grams of the product of Example 14 were added to 2cups of hot water. The mixture was cooked for 12 minutes at the highsetting, stirring 5 and 10 minutes into the cooking process. Anacceptable product resulted, although, without draining, the product hadexcess water.

In Example 23, 123 grams of the product of Example 17 were added to 11/2cups of hot water, which mixture was cooked for 10 minutes on high,stirring 5 minutes into the cooking process. The product was acceptable,although slightly sticky, indicating too little water had been used.

In Example 24, 123 grams of the product Example 20, 13/4 cup hot water,and one teaspoon of sunflower oil were subjected to the same cookingprocess as in Example 23. The product which resulted was veryacceptable.

CONCLUSIONS

The present invention thus provides a method and an extrusion die platecapable of preparing extruded pasta products which are microwavecookable in non-boiling water. Unlike other processes for producing coldwater tolerant pasta shapes, the present process is relatively much moreeconomical in terms of time and cost effectiveness; existing extrusionapparatuses may be easily modified in accordance with the presentinvention.

In addition to desirably low starch losses after exposure to non-boilingwater, the process and extrusion die plate of this invention conferother desirable properties on the pasta so produced, including superiorcolor and texture. Also, the process of the invention is accomplished atlower extrusion head pressures; higher production rates (at given poweruse levels); and decreased power use, all relative to prior artprocesses. Each of these factors adds to the economy of the claimedprocess relative to the prior art.

While the invention has been disclosed by reference to the details ofpreferred embodiments, this disclosure is intended in an illustrativerather than in a limiting sense, as it is contemplated thatmodifications will readily occur to those skilled in the art, within thespirit of the invention and the scope of the appended claims.

What is claimed is:
 1. An extrusion die plate for forming shapedalimentary pastes, said plate being formed with a plurality of orifices,each defined respectively by a surface;wherein said die plate comprisesmeans for heating said plate; wherein a portion of said surface of eachof said orifices of said die plate has a coating thereon and whereinanother portion of said surface of each of said orifices is uncoated,such that heat transfer to a paste being extruded through said orificesis substantially inhibited within said portion of said surfaces of eachsaid orifices having the coating and heating of said paste occurssubstantially only in the uncoated portion of said surface of each ofsaid orifices.
 2. An extrusion die plate according to claim 1 whereinsaid orifices have progressively smaller cross sections in the directionof extrusion.
 3. An extrusion die plate according to claim 1 whereinheat transfer to a paste being extruded is substantially inhibited untilthe cross section of the orifices has reached its smallest value.
 4. Anextrusion die plate according to claim 1 wherein said coating isdisposed on all but about the last 10% to 25% of the surface of each ofsaid orifices in the direction of extrusion.
 5. An extrusion die plateaccording to claim 1 wherein said die is heated by means of electricalresistance heating.
 6. An extrusion die plate according to claim 1wherein the orifice coating material is a plastic material having a lowcoefficient of friction and low thermal conductivity.
 7. An extrusiondie plate according to claim 6 wherein said coating material is selectedfrom the group consisting of polytetrafluoroethylene,polyvinylidenefluoride, and mixtures thereof.